Ewald Schlüter

Penta(methoxycarbonyl)cyclopentadienyl-substituted germanium(II) and tin(II) compounds. X-ray crystal structure of bis[penta(methoxycarbonyl)cyclopentadienyl]tin(II)

Abstract Reaction of decamethyl-germanocene or -stannocene with equimolar amounts of penta(methoxycarbonyl)cyclopentadiene leads to the ionic compounds pentamethylcyclopentadienylgermanium-penta(methoxycarbonyl)cyclopentadienide (3) and pentamethylcyclopentadienyltin-penta(methoxycarbonyl)cyclopentadienide (4), in which pentamethylcyclopentadienyl-germanium and -tin cations are present together with the penta(methoxy)cyclopentadienide anion. A molar ratio of 1 2 yields the covalent bis[penta(methoxycarbonyl)cyclopentadienyl]-germanium(II) (5) or -tin(II) (6). Crystals of the tin compound 6 are orthorhombic, space group P21212 with a 15.656(2), b 15.424(2), c 7.033(1) A and Z = 2. The structure of 6 was solved via the heavy-atom method and refined to R = 0.037 using 1098 diffractometer data with I ⩾ 1.5σ(I). The tin atom, which lies on the two-fold axis, has four-fold oxygen coordination from carbonyl oxygen atoms of two methoxy carbonyl groups on each of two ligands, with SnO distances of 2.240(9) and 2.271(9) A. The compounds 5 and 6 are fluxional in solution.

SYNTHESIS OF TRIMETHYLSILYLATED GERMANOCENES - X-RAY STRUCTURE OF AND STERIC EFFECTS IN HEXAKIS(TRIMETHYLSILYL)GERMANOCENE

Abstract Reaction of GeCl2 · dioxane with mono-, bis- and tris-(trimethylsilyl)cyclopentadienyllithium yields bis-, tetrakis- and hexakis-(trimethylsilyl)germanocene. A single-crystal X-ray diffraction study shows the metallocene species with six silyl groups to consist of nearly parallel C5-units, bound symmetrically to the germanium center. The eclipsed conformation of the rings and the 1,2.4-silyl substitution pattern leave only two silyl groups face to face, effecting a small bending of the molecule. The molecular structure has been examined with the steric energy program EENY2. The conformation found in the crystal is close to the lowest minimum given by the calculations.

Zur synthese von trimethylsilylsubstituierten plumbocenen

Abstract The reaction of silylated cyclopentadienyllithium compounds with lead(II) chloride yields the yellow, crystalline plumbocenes I, II and III with two, four and six trimethylsilyl groups. The stability of these π-complexes against oxidation and thermal decay increases with increasing number of silyl substituents.

Introduction of the pentakis(methoxycarbonyl)-cyclopentadienyl ligand in stannocene chemistry

Abstract Decamethylstannocene reacts with pentakis(methoxycarbonyl)cyclopentadiene with elimination of pentamethylcyclopentadiene, yielding pentakis(methoxycarbonyl)pentamethylstannocene and decakis(methoxycarbonyl)stannocene.